How do you encode a chess move in a neural network?
The number is 4672 from Google.


  https://arxiv.org/pdf/1712.01815.pdf


A move in chess may be described in two parts: selecting the piece to move, and then
selecting among the legal moves for that piece. We represent the policy π(a|s) by a 8 × 8 × 73
stack of planes encoding a probability distribution over 4,672 possible moves. Each of the 8×8
positions identifies the square from which to “pick up” a piece.


4672 might sound a big number but it's nothing to what Google (and many other competitors) has been doing to deep learning for image analysis.